The Environmental Protection Agency (EPA) recently proposed rules that require refineries to conduct continuous monitoring of facility boundaries to determine average concentration of a specific air toxic, specifically benzene. One method outlined in the rules, Method 325A, describes the field or implementation process used at or inside a facility property boundary or from fugitive and area emission sources using passive or diffusive tube samplers (PS). The concentration of airborne volatile organic compounds (VOCs) from fugitive-emission or area-emission sources may be determined using this method, in combination with a companion method, Method 325B.
Companion Method 325B describes requirements for sample preparation and analysis. For example, Method 325B describes the laboratory preparation of sampling tubes, shipment and storage of exposed sampling tubes, and analysis of sampling tubes collected using either the passive sampling procedure or an alternative active, or pumped, sampling method. Method 325B further describes the use of thermal desorption and gas chromatography (TD/GC) analysis of VOCs from fugitive-emission and area-emission sources collected onto sorbent tubes using passive sampling, outlined by Method 325A. Methods 325A and 325B are valid for the measurement of benzene.